As described in U.S. Pat. No. 4,176,654 of Zinn, it is known to make a tube mat of a solar collector from a plurality of individual tube strips each formed by a group of parallel flexible tubes joined laterally to one another at spaced-apart locations along their lengths. The tubes may be of oval or flattened section and may be interconnected by flat webs.
In such an arrangement it is standard to connect every other tube at one end of the mat to an intake manifold and to connect the remaining alternate tubes at this one end to an output manifold, while at the opposite mat end U-shaped shunts connect alternate tubes together. Such an arrangement is typically cemented atop a bed of insulation on a roof within an insulating curb, and a transparent cover is provided above the tube mat to protect the tubes from the elements and afford further insulation.
While the use of such a tube mat substantially eases the work of installing a solar collector on a roof or similar surface by making it possible to provide a collector of virtually any desired size, cut to fit on the job, it still has some disadvantages. In particular, although the tubes are connected together to one another within each strip, it is necessary to position adjacent strips--as each such strip is rarely more than, say, 8 in wide--very carefully to avoid the cement that adheres them to the support surface from oozing up between adjacent strips. As a result of this problem, the tendency is to make the strips as wide as possible to reduce the number of longitudinally extending joints in a single mat. Such increase in width in part reduces the adaptability of the basic tube-mat strip to collectors of different widths, it being necessary to use a certain rather wide basic modular width.